Domestic wastewater treatment systems are a common method of dealing with household waste in areas without sewer connections. This usually involves on-site disposal of the treated or partially treated effluent. Recycling of water from these systems for use in the home, whilst highly desirable, has been hampered by the variable quality of the treated effluent and difficulty of ensuring safe water for reuse.
A typical biolytic filtration system is described in U.S. Pat. No. 5,633,163. The biolytic filtration system comprises simultaneously treating wastewater and solid organic waste within a common filter bed having a top, a bottom, and a continuum of layers of decomposing and decomposed solid organic waste. The degree of decomposition of the solid organic waste in the filter bed increases from the top of the filter to the bottom with there being complete decomposition of the solid organic waste at the bottom of the bed. The filter bed incorporates a supply of living organisms which maintain the filter bed in an air and liquid permeable condition. Wastewater and solid organic waste are applied to the upper layer of the filter bed so that the wastewater percolates through the filter bed. The filter bed is maintained in an aerobic condition and treated wastewater is drawn from the bottom of the filter bed in a substantially purified state. Adding a membrane to the treatment process can greatly improve the water quality and provide pathogen removal, making reuse a viable option.
As the filtration system is likely to be used in a domestic situation or in a remote isolated area, it is desirable to provide a membrane filter which is integrated inside the treatment tank making it compact and is self-backwashing, without the need for sophisticated controllers, valves and timers. The control operations of the system are desirably performed by simple components such as hydraulic and non-return valves and pumps with the only controls required being float or level switches to control the pump operation. Further, given the limited opportunity to effectively dispose of backwash waste in domestic situations, it is desirable that backwash waste be further treated by recycle back to the filter bed.